1. Field of the Invention
The invention relates to an automotive construction machine, in particular to a slipform paver or a road milling machine. The invention also relates to a method for controlling an automotive construction machine, in particular for controlling a slipform paver or a road milling machine.
2. Description of the Prior Art
Known slipform pavers are known for the continuous production of building structures from a flowable material. They have a device in which the flowable material is brought into the required form. A device of this type for forming the flowable material is also known as a concrete mold. Concrete guide walls for example can be produced on the ground by slipform pavers. Known road milling machines have a milling drum which mills material off the ground.
Known slipform pavers and road milling machines have a chassis which comprises at least one front and rear running gear in the working direction, and a machine frame on which the device for forming flowable material is provided or on which the milling drum is provided. The machine frame is supported by the lifting system associated with the running gear, so that the machine frame and running gear are movable relative to one another and thus the height and orientation of the machine frame is adjustable with respect to the ground. The concrete mold and the milling drum are fastened to the machine frame so that they are vertically adjustable with respect to the ground. The running gear can be crawler tracked running gear or wheels.
A slipform paver is known for example from WO 2011 026 504 A1 (U.S. Pat. No. 8,496,400) and a road milling machine is known for example from EP 2 104 768 B1 (U.S. Pat. No. 8,424,972).
As the construction machine advances, the machine frame should have a parallel orientation to the ground surface, seen in the longitudinal direction. The orientation in the transverse direction is determined by the respective case of use and is often also parallel to the ground surface. In this context, “ground surface” is understood as an idealised flat surface which is free from any unevenness and which can be inclined with respect to the horizontal in the longitudinal and/or transverse direction. However, in practice, the surface of the ground will exhibit unevennesses, i.e. it will not be flat.
The construction machine known from EP 2 104 768 B1 (U.S. Pat. No. 8,424,972) has a control unit which can retract or extend the lifting systems associated with the running gear such that the machine frame remains in a parallel orientation to the ground surface. A control unit of this type can also be provided on a slipform paver.
In a slipform paver, the concrete mold fastened to the machine frame is guided over the ground as the construction machine advances. The underside of the concrete mold is open and the sides of the mold are delimited by side plates. The top of the mold is delimited by a cover plate. The flowable material issues at the rear of the mold. In the mold, the concrete is compacted between the cover plate and the side plates on the one hand and between the cover plate and the ground on the other hand before it emerges at the rear of the mold in the desired form.
As the slipform paver advances, the cover plate of the concrete mold should always be at the same height with respect to the ground, so that the building structure, for example the guide wall is always at the same height in the longitudinal direction. To adjust the height of the concrete mold with respect to the ground, the lifting systems are extended and retracted so that the mold is raised or lowered with the machine frame.
Adjusting the height of the machine frame proves to be relatively easy on flat ground. However, if the ground is not flat, the height of the mold has to be corrected with respect to the surface of the ground as the construction machine advances. A correction in height is also necessary because the running gear do not run in the same track in which the building structure is erected. In this respect, various solutions are known in the prior art. One solution which is simple, economical and frequently used is to scan the surface of the ground with suitable contacting or contact-free sensors to adjust a constant distance of the concrete mold from the ground surface. However, a disadvantage of this solution is that possible unevennesses of the ground surface are “copied”, because the upper edge of the building structure is always at a constant distance from the actual surface of the ground so that the unevennesses of the ground surface are transferred to the building structure.
To solve this problem, in the prior art stringlines are used which are tensioned at a predetermined height and in a predetermined orientation above the ground with the purpose of representing the desired course of the building structure. To compensate for the irregularities in the ground surface, this building structure should have different heights in the longitudinal direction, i.e. where there is a depression in the ground, it should have a greater height and where there is an elevation of the ground, it should have a lower height so that the upper edge of the building structure is always at the same height in the longitudinal direction.
It is a disadvantage that the stringlines have to be previously tensioned and calibrated which is time-consuming and expensive. Furthermore, the tensioned stringlines obstruct the operation of the building site. In the case of a slipform paver, if a stringline is not used, irregularities in the ground, for example elevations or depressions which occur in portions can therefore result in fluctuations in height of the building structure in the longitudinal direction. The same problem arises in the case of a road milling machine, because the height of the machine frame with respect to the surface of the ground determines the milling depth.